Fluid pressure system



8- 1941- E. F. LOWEKE 2.253.240

FLUID PRESSURE SYSTEM Filed Sept. 10. 1938 2 Sheets-Sheet 2 ATTORNEY.

Patented Aug. 19, 1941 FLUID PRESSURE SYSTEM Erwin F. Loweke, Detroit,Mich., assignor to Bydraulic Brake Company, Detroit, Mich., acorporation of California ApplicationSeptemberlO, 1938, Serial No.229,365 (c1. era-54.5)

' 4 Claims.

. This invention relates to fluidpressure braking systems, and moreparticularly to duplex braking systems for motor vehicles.

An object of the invention is to providea fluid pressure braking systemfor a motor vehicle including independent fluid pressure braking-systems, one for actuating the brakes associated .with the front wheelsof a vehicle, and another sure in the systems.

Yet another object of the invention is to provide aduplx fluid pressurebraking system includingmeans for actuating both systems in unison,means compensating for a differential of pressure in the systems, andmeans for maintaining one of the systems operativein the event offailure of the other system.

A feature of the invention is a cylinder and a piston movable in thecylinder having spaced heads, and a chamber between the heads havingtherein a diaphragm for equalizing the pressure created in the cylinderforward of the respective heads.

' Other objects and features of the invention will appear from thefollowing description taken in connection with the drawingsforminga-part of this specification, and in which-- Fig. 1 is adiagrammatic view of a fluidpressure braking system embodying theinvention;

Fig. 2 is avertical sectional viewof the fluid pressure producingdevice; 3

Fig. 81s a fragmentary'view illustrating the diaphragm; and V Fig. 4 isan end elevation partly in section.

Referringto the drawings for more specific details of the invention,lll' represents a; fluid pressure producing device includingsubstantially corresponding reservoirs l2 and I4 each having a fillingopening IE and I8 normally closed as by a plug .20 and 22 provided withopenings 24 and 26 therethrough for venting the reservoirs to theatmosphere. y

A cylinder 28 at the base of the reservoir includes a large chamber 30and a relatively small chamber 32 arranged forward of the large chamberconcentrically thereto and in direct communication therewith. The largechamber is open at its, rear end, and arranged inits wall are ports 34and 36 providing communications ".l-betw'een' the large chamber and thereservoir. The large chamber also ha a discharge port 38 I controlled asby a two-way valve 40. The small chamber is closed as by a head 42provided with a discharge port 44 controlled as by a two-way valve 46,and arranged in the wall of the small chamber are ports 48 and 50providing communications between the small chamber and the reservoir.

A fluid pressure delivery pipe or conduit 52 connected to the dischargeport 38 has branches connected respectively to fluid pressure actuatedmotors 54 arranged for the actuation of a pair. of brakes, and,correspondingly, a fluid pressure delivery pipe or conduit 56 connectedto the discharge port 44 has branches connected respectively to fluidpressure actuated motors 58 arranged for the actuation of another pairof brakes. As shown, the fluid pressure actuated motors 54 and 58 arearranged in pairs, one pair for actuating the brakes associated with thefront wheels of the vehicle and another pair for actu-. ating the brakesassociated with the rear wheels of the vehicle.

. The brakes are of a conventional type including a fixed support orbacking plate 60 adapted to be secured to an axle or to an axle housing,a rotatable drum 62' associated with the backing plate adaptedto besecured to a wheel, a pair of corresponding interchangeable frictionelements or shoes 64 pivoted on the backing plate for cooperation withthe drum, a r'etractile spring 66 connecting the shoes, and a motorcorresponding to the motors 54and 58 mounted'on the backing plate andconnected to the shoes for actuating the shoes into engagement with thedrum against the resistance of the retractile spring.

A piston 68*reciprocable in the chamber 38 is held against displacementby a washer l8 seated on an annular shoulder in the wall of the chamberadjacent the open end thereof, and secured in place by a retaining ring12 seated in a groove in the wall of the chamber. The piston 68 includesa head 14, a reduced body portion 16 providing in conjunction with thewall of the chamber 30 an annular chamber 18 communicating with thereservoir l2 by way of the port 38, and

a skirt having therein a socket 82 extending well into the body of thepiston. The skirt carries a sealing cup 84 inhibiting the seepage offluid from the annular chamber past the piston, and the head has aplurality of passages 86 therethrough providing comunications betweenthe annular chamber 18 and that portion of the chamber 30 forward of thepiston, and a sealing cup 88 supported on the head controls the"passages.

A concentric extension 90 on the head of the piston supports anequalizing chamber 92. As shown, the extension is provided in its facewith a semi-spherical concavity 94 communicating at its bottom with astrangulated recess 98, and a plurality of passages 98 through theextension providing communications between the concavity 94 and thechamber 30 of the cylinder.

A force transmitting rod I has an enlarged end I02 provided with asemi-spherical concavity I04 corresponding to the concavity in the faceof the extension 90. The rod has an axial bore I08 communicating withthe concavity I04, at its bottom, and the communication is strangulatedas indicated at I08. The rod also has a plurality of passagestherethrough providing communications between the concavity I04 and theaxial bore I 08. A flange IIO on the enlarged head I02 of the rod I00 isattached to the extension 90 on the head of the piston 88 so as tosupport the rod concentrically of the piston with the concavity I04 inthe head of the rod in oppositely disposed relation to the concavity 94in the extension 90.

The flange II 0 on the head of the rod has a groove I I2, and a flexiblediaphragm II 4 has a rim seated in the groove and secured againstdisplacement by the oppositely disposed rims of the concavities 94 andI04. As shown, the diaphragm has arranged centrally thereonoppositelydisposed flexible buttons H8 and H8 adapted to enter respectively thestrangulated recess 98 and the strangulated communication I08 upon anexcessive differential of pressure in the concavities 94 and I04 so thatthe diaphragm may be retained in flexed position against the wall of theconcavity in which loss of pressure occurs.

A piston I reciprocable in the small chamber 32 is attached to the forcetransmitting rod I00, and a washer I22 sleeved on the rod supports asealing cup I24 retained against displacement by a spring I28 interposedbetween the cup and the enlarged head I02 of the rod. This cup inhibitsseepage of fluid from the chamber 30 into the chamber 32. The piston I20has an axial bore communicating with the passage I08 in the rod I00. Thepiston includes a head I28, a reduced body portion I30 providing inconjunction with the wall of the chamber 32 an annular chamber I32communicating with the reservoir I4 by way of the port 44, and a skirtI34 supportingasealing cup I38 for inhibiting seepage of fluid from theannular chamber I32 past the skirt I34 of the piston.

The head of the piston I20 has a plurality of passages I38 therethroughproviding communications between the annular chamber I32 and thatportion of the chamber 32 forward of the piston. A sealing cup I40seated on the head of the piston controls the passages I38, and a springI42 interposed between the cup and the two-way valve 48 serves to retainthe cup and valve against displacement and also to return the piston toretracted position.

A thrustpin I 44 has one of its ends seated in the socket 82 in thepiston 88 and its other end attached to a coupling I48, and the couplingis connected as by a flexible boot I48 to the open end of the cylinderfor the exclusion of dust from-the cylinder. A rod I50 has one of itsends attached to the coupling I48 and its other end is pivotallyconnected to a foot pedal lever I52 rockable on the shaft I54 andconnected by a retractile spring I58 to a. fixed support I58.

In a normal operation vof the systemf-upon depressing the foot pedallever I52, force is transmitted from the lever through the rod I50 andthe thrust pin I44 to the piston 88, resultin in movement of the piston88 on its compression stroke and also advancing the piston I20 connectedto the piston 88. During the initial movement of the piston 88, thesealing cup 88 on the head thereof closes the port 38, and, thereafter,as the piston advances, pressure is imposed on the fluid in that portionof the chamber 30 forward of the piston. This results in displacement offluid from the chamber 30 through the port 38, past the two-way valve40, and through the fluid pressure delivery pipe or conduit 52 into thefluid pressure actuated motors 54, causing energization of the motors.This results in movement of the shoes 84 into engagement with the drum62 against the resistance of the retractile spring 88. correspondingly,during the initial movement of the piston I20, the cup I40 on the headthereof closes the port 50, and, thereafter, as the piston advances,pressure is imposed on the fluid in that portion of the chamber 32forward of the piston, resulting in displacing fluid from the chamber32, past the two-way valve v48, through the discharge port 44 and fluidpressure delivery pipe or conduit 58 into the fluid pressure actuatedmotors 58, causing energization of the motors 58, and resulting inmovement of the shoes 84 into engagement with the drum 82 against theresistance of the retractile springs 88.

Under normal conditions, variations of pressure may be produced in therespective chambers 30 and 32, due to a differential in the adjustmentof the respective pairs of brakes associated with the front and rearwheels of the vehicle, and in order to compensate for this differentialof pressure, so that both pairs of brakes may be applied with equaleffectiveness, a compensating means is arranged intermediate the pistons88 and I20.

This compensating means includes opposed concavities 94 and I04, eachhaving in its bottom a strangulated opening 98 and I08. The concavity 94communicates with the chamber 30 as by passages 98, and the concavity I04 communicates with the chamber 32 as by suitable passages and the boreI 08 through the rod I00 and the axial bore of the piston I20. Aflexible diaphragm II4 clamped between the rims of the concavities maybe flexed to compensate for any variation of pressure in theconcavities, and the diaphragm has oppositely disposed flexible buttonsI I8 and '8 adapted, upon an excessive differential of pressure in theconcavities, to enter the strangulated opening in the bottom of theconcavity in which loss of pressure has occurred, and thus secure thediaphragm against the wall of this cavity.

Upon conclusion of a braking operation and release of the foot pedallever I52, the lever is returned 'to its retracted position under theinfluence of the retractile spring I58- This movement of the leverretracts the rod I50 and the thrust pin I44, and results in release ofthe pistons, whereupon the spring I42 becomes effective .to return thepistons to their retracted position.

As the piston 88 returns to its retracted position, a partial vacuum iscreated in the chamber 30. This results in drawing fluid from thereservoir I 2, through the port 34 into the annular chamber I8, thencethrough the passages 88, past the sealing cup 88, into the chamber 30,completely filling the chamber. correspondingly, as the piston I20returns to its retracted position, a partial vacuum is created in thechamber 32,

and this results in drawing fluid from the reservoir l4 through theport48 into the annular chamber I32, thence through the passages I33,past'the sealing cup I40, into the chamber 32, completely fllling thechamber.

During this period of the operation, fluid is returning to the chambers30 and 32 from the fluid pressure actuated motors 54 and 58, and

the fluid pressure delivery pipes connecting the motors to the chambers30 and 32, under the influence oi the retractile springs connecting theshoes of the respective brakes. Under these conditions, the chambers 30and 32'receive fluid in excess of their respective capacities, and thisexcess fluid is displaced from the respective chambers through the ports36 and'50 into the reservoirs l2 and I4.

In the event of failure of the system for actuating the set of brakesfor the front wheels of the vehicle, the piston 63 becomes ineffectivefor viding the chamber adapted to flex and lie on I producing pressure,and, accordingly, the diaphragm H4 flexes excessively and the button IIt on the diaphragm enters the strangulated recess 9 6 and secures thediaphragm against further movement. n subsequentoperations, the.

piston 68 merely serves as a mechanical means for advancing the pistonI20. In the event or failure of the system for actuating the set. of

, brakes for the rear wheels, the piston I becomes ineffective forproducing pressure, and, accordingly, due to a difierential-oi pressuresin the systems, the diaphragm is flexed so that the button H8 enters thestrangulated opening I08 and secures the diaphragm against further move-7 ment.

While this invention has been described in connection with certainspeciflc embodiments, the

principle involved is susceptible of numerous other applications thatwill readily occur to persons skilled in the art. The invention is,therefore, to be limited only as indicated by the scope of the appendedclaims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is- 1. A fluidpressure equalizer comprising a chamber having opposite openings foradmission of fluid to the chamber, a flexible diaphragm dividing thechamber, and oppositely disposed flexible members on the diaphragmadapted to enter and close the openings and to latch therein.

the face of either concavity, and oppositely disposed flexible memberson the diaphragm adapted to enter and lock in the strangulated openings.

4. A fluid pressure braking system comprising independent fluid pressure'producing means connected for simultaneous actuation, a single actuatorfor both pressure producing means, a

fluid Pressure-actuated motor connected to each pressureproducing means,a braking element connected 'to each motor, an equalizing chamberincluding opposed concavities communicating with the respective pressureproducing means,

, each of the concavities having a strangulated opening, a flexiblediaphragm separating the concavities, and flexible buttons on thediaphragm adapted to enter and lock in the open- ,ings upon creation ofan abnormal difierential of pressure in the equalizing chamber. 7

